The repair and maintenance of underground gas mains has long been a problem for municipalities. In particular, to repair a leaking gas main, the precise area of the leak must be located, and then the earth surrounding the leaking pipe must be excavated. The excavation process is time consuming, costly and a nuisance to the public if use of a busy street is interrupted.
The most common location for a leak in a gas main is at a joint between two adjoining pipes. Typically, a joint of a gas main includes a bell-shaped female end in which a straight male end is inserted. Jute, or fibrous material, is inserted inside the heel of the bell. The distal end of the male pipe engages the jute which serves as a seal between the bell-shaped female member and the end of the male member. A relatively permanent seal is provided by the insertion of lead, concrete or other material inside the bell between the inside surface of the bell and the outside surface of the male pipe.
The problem with the above-referenced gas main design is that it will eventually leak. The condition of the jute material will degrade over time thereby enabling gas to escape through the jute before coming in contact with the lead or cement. The lead or cement will also degrade with time and a perfect seal may not have been obtained during the initial installation. The result is a leaking gas main joint which, until now, would have to be excavated to be successfully repaired.
The prior art teaches three primary methods for fixing a leaky joint in a gas main, all of which are problematic. One method would be to excavate the leaky joint and clamp an external seal to the joint or apply a heavy coat of sealant to encapsulate the outside surface of the leaky joint. Of course, this method is inherently expensive due to the excavation costs, which often involve the excavation in the middle of a busy street.
In addition to clamping an external seal or applying a heavy coat of sealant to the outside of the joint area, another method involves drilling a hole into the joint and injecting sealant into the joint space. Of course, this method also involves a costly excavation which, if possible, is to be avoided.
As opposed to the above methods, one internal method has been developed which involves the use of a snake with a spray nozzle disposed at a distal end thereof. The snake is fed into the gas main and the nozzle sprays a thin coat of anaerobic sealant onto the joint. However, because the sealant must be sprayed, the sealant must also have a thin consistency or low viscosity. Low viscosity sealants are simply ineffective at repairing deteriorated jutes and large cracks because a thicker, more viscous sealant is required for these types of repairs. Accordingly, if the jute is relatively damaged or if large cracks or deteriorated pipe is present, the spray system taught by the prior art is simply insufficient.
Accordingly, there is a long-felt need for an apparatus and method for delivering thick sealant to the inside surfaces of gas mains and other pipes for the repair of leaky joints, cracks and corroded portions of the gas mains or pipes. The method and apparatus should also preferably eliminate or at least minimize the need for excavation.